Polymer–ion–clay interaction based model for ion conduction in intercalation-type polymer nanocomposite

A series of polymer nanocomposite films based on intercalation of (PAN)₈LiCF₃SO₃ into the nanometric clay channels of an organomodified clay has been prepared using the standard solution-casting technique. The role of organoclay concentration on polymer–ion interaction, ion–ion interaction, and ion–clay interaction in clay-based nanocomposite films has been analyzed using Fourier transform infrared (FTIR) analysis. Substantial ion dissociation is observed even at a very low clay loading (1–2 wt.%) in the nanocomposites. FTIR results suggest the presence of both uncoordinated CF₃SO₃ ⁻ (free-anions) and ion pairs in the nanocomposite evidenced by changes in CF₃SO₃ ⁻ symmetry from C3ν to Cs and marked asymmetry in the profile of degenerate δ_d(CF₃ ⁻) mode. The experimental results suggest a direct correlation of clay-assisted ion dissociation process with variation in conductivity (σ _dc) and glass transition temperature (T _g) as a function of clay concentration. A model has been proposed to explain the observed correlation on the basis of polymer–ion–clay interaction. The proposed scheme of ion transport mechanism appears to be consistent with the experimental observation.     

Structural and electrical properties of lanthanum-substituted lead titanate ceramics

The effect of lanthanum substitution on the structural, dielectric and piezoelectric properties of lead calcium titanate (PCT) ceramics is studied. Samples with compositional formula Pb_{0.76? x} La _x Ca_0.24Ti_0.98Mn_0.02O₃ (PLCT) (x?=?0–0.08, in steps of 0.02) were prepared by the conventional dry ceramic technique. Phase and structural analysis was carried out using XRD and SEM respectively. X-ray analysis confirmed the formation of single-phase compound with tetragonal crystal structure. Dielectric properties were studied in detail as a function of frequency and temperature. The Curie temperature (T _C) and tetragonality (c/a) was found to decrease with increase in lanthanum content. The Curie temperature was also confirmed from the thermal-expansion behaviour of the sintered samples. Piezoelectric coefficients (d ₃₃, d ₃₁, g ₃₃, g ₃₁, g _h, d _h, k _t and k _p) were measured at room temperature. From this study it is found that La³⁺ substitution helps in the improvement of electro-mechanical anisotropy.     

An analysis of phase-modulated heteronuclear dipolar decoupling sequences in solid-state nuclear magnetic resonance

The design of variants of the swept-frequency two-pulse phase modulation sequence for heteronuclear dipolar decoupling in solid-state NMR is reported, their performance evaluated, and compared with other established sequences like TPPM and SPINAL. Simulations performed to probe the role of the homonuclear (1)H-(1)H bath show that the robustness of the decoupling schemes improves with the size of the bath. In addition, these simulations reveal that the homonuclear (1)H-(1)H bath also leads to broad baselines at high MAS rates. Results from a study of the SPINAL decoupling scheme indicate that optimisation of the starting phase and phase increment improves its performance and efficiency at high MAS rates. Additionally, experiments performed on a liquid crystal display the role of the initial phase in SPINAL-64 and sequences in the SW(f)-TPPM family.     

Synthesis,characterization & in vitro antimicrobial‐antioxidant studies of novel N,1‐diphenyl‐4,5‐dihydro‐1H‐1,2,4‐triazol‐3‐amine derivatives

A new series of 1,2,4‐triazole was designed, synthesized, and characterized as remarkable antimicrobial and antioxidant agents. These heterocycles have been prepared from the cyclization reactions of Schiff bases 3 ( a‐k ) with phenylhydrazine by refluxing under the alkaline medium. The Schiff bases in turn were realized in good yields from the condensation reactions of N‐phenylurea with different aromatic aldehydes. The structures of the intermediates 3 ( a‐k ) and final heterocycles 4 ( a‐k ) have been fully characterized through their spectral parameters.     

210Po in the environment: insight into the naturally occurring polonium isotope

Journal of Radioanalytical and Nuclear Chemistry - Polonium is rapidly emerging as an international environmental health concern primarily because of the recent rise in hydraulic fracturing...     

Nitrile Metabolizing Enzymes in Biocatalysis and Biotransformation

Nitrile metabolizing enzymes, i.e., aldoxime dehydratase, hydroxynitrile lyase, nitrilase, nitrile hydratase, and amidase, are the key catalysts in carbon nitrogen triple bond anabolism and catabolism. Over the past several years, these enzymes have drawn considerable attention as prominent biocatalysts in academia and industries because of their wide applications. Research on various aspects of these biocatalysts, i.e., sources, screening, function, purification, molecular cloning, structure, and mechanisms, has been conducted, and bioprocesses at various scales have been designed for the synthesis of myriads of useful compounds. This review is focused on the potential of nitrile metabolizing enzymes in the production of commercially important fine chemicals such as nitriles, carboxylic acids, and amides. A number of opportunities and challenges of nitrile metabolizing enzymes in bioprocess development for the production of bulk and fine chemicals are discussed.     

A classification theorem for Albert algebras

Let be a field whose characteristic is different from 2 and 3 and let be a quadratic extension. In this paper we prove that for a fixed, degree 3 central simple algebra over with an involution of the second kind over , the Jordan algebra , obtained through Tits' second construction is determined up to isomorphism by the class of in , thus settling a question raised by Petersson and Racine. As a consequence, we derive a ``Skolem Noether' type theorem for Albert algebras. We also show that the cohomological invariants determine the isomorphism class of , if is fixed.